Because these products are essentially "equivalent" to approved products already being marketed, they "do not raise new questions of public health" and can be sold to U.S. consumers, explained Mitchell Zeller, director of FDA's Center for Tobacco Products.

He stressed that allowing the sale of these cigarettes does not mean that they are safer or less harmful than cigarettes already on the market.

"An FDA product order is not a finding by the FDA that the product is considered safe or safer than its predicate product, or less harmful in general," he said. "In addition, the companies cannot say their products are 'FDA-approved.'"

The agency rejected four new tobacco products because they determined that they were not similar enough to existing products already on the market.

"The applicant [also] did not adequately show that the new product did not raise new questions of public health," Zeller said at the news briefing.

By law, the FDA cannot release the names of the manufacturers of the rejected products or what types of products they were, he added.